Re: [PATCH v2] gpio: mt7621: support gpio-line-names property

[Sergio Paracuellos <sergio.paracuellos@gmail.com>]

Hi Andy,

On Sat, Jul 3, 2021 at 1:32 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
>
> On Sat, Jul 3, 2021 at 2:06 PM Sergio Paracuellos
> <sergio.paracuellos@gmail.com> wrote:
> > On Fri, Jul 2, 2021 at 1:30 PM Sergio Paracuellos
> > <sergio.paracuellos@gmail.com> wrote:
>
> ...
>
> > -               ret = devprop_gpiochip_set_names(gc);
> > +               ret = devprop_gpiochip_set_names(gc, 0);
>
> I had been expecting that this parameter would be in the field of the gpiochip.
>
> ...

If doing it in that way is preferred, I have no problem at all. But in
that case I think there is no need for a new
'devprop_gpiochip_set_names_base' and we can assume for all drivers to
be zero and if is set taking it into account directly in
devprop_gpiochip_set_names function? Is this what you mean by having
this field added there??

>
> > The problem I see with this approach is that
> > 'devprop_gpiochip_set_names' already trusts in gpio_device already
> > created and this happens in 'gpiochip_add_data_with_key'. So doing in
> > this way force "broken drivers" to call this new
> > 'devprop_gpiochip_set_names_base' function after
> > 'devm_gpiochip_add_data' is called so the core code has already set up
> > the friendly names repeated for all gpio chip banks and the approach
> > would be to "overwrite" those in a second pass which sounds more like
> > a hack than a solution.
> >
> > But maybe I am missing something in what you were pointing out here.
>
> Would the above work?

The following works for me, but the overwritten part of the
'gdev->descs[i].name' because this has been already called once by the
core code is hacky and dirty, IMHO :)

diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 4a7e295c3640..ad145ab0794c 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -537,6 +537,8 @@ extern int gpiochip_add_data_with_key(struct
gpio_chip *gc, void *data,
        devm_gpiochip_add_data_with_key(dev, gc, data, NULL, NULL)
 #endif /* CONFIG_LOCKDEP */

+extern int devprop_gpiochip_set_names_base(struct gpio_chip *gc, int base);
+
 static inline int gpiochip_add(struct gpio_chip *gc)
 {
        return gpiochip_add_data(gc, NULL);

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 6e3c4d7a7d14..f9942d5d2f2a 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -361,13 +361,14 @@ static int gpiochip_set_desc_names(struct gpio_chip *gc)
 /*
  * devprop_gpiochip_set_names - Set GPIO line names using device properties
  * @chip: GPIO chip whose lines should be named, if possible
+ * @base: starting index in names array to start copying from
  *
  * Looks for device property "gpio-line-names" and if it exists assigns
  * GPIO line names for the chip. The memory allocated for the assigned
  * names belong to the underlying software node and should not be released
  * by the caller.
  */
-static int devprop_gpiochip_set_names(struct gpio_chip *chip)
+static int devprop_gpiochip_set_names(struct gpio_chip *chip, int base)
 {
        struct gpio_device *gdev = chip->gpiodev;
        struct device *dev = chip->parent;
@@ -383,12 +384,18 @@ static int devprop_gpiochip_set_names(struct
gpio_chip *chip)
        if (count < 0)
                return 0;

-       if (count > gdev->ngpio) {
+       if (count > gdev->ngpio && base == 0) {
                dev_warn(&gdev->dev, "gpio-line-names is length %d but
should be at most length %d",
                         count, gdev->ngpio);
                count = gdev->ngpio;
        }

+       if (count <= base) {
+               for (i = 0; i < count; i++)
+                       gdev->descs[i].name = "";
+               return 0;
+       }
+
        names = kcalloc(count, sizeof(*names), GFP_KERNEL);
        if (!names)
                return -ENOMEM;
@@ -401,14 +408,21 @@ static int devprop_gpiochip_set_names(struct
gpio_chip *chip)
                return ret;
        }

+       count = (base >= count) ? (base - count) : count;
        for (i = 0; i < count; i++)
-               gdev->descs[i].name = names[i];
+               gdev->descs[i].name = names[base + i];

        kfree(names);

        return 0;
 }

+int devprop_gpiochip_set_names_base(struct gpio_chip *gc, int base)
+{
+       return devprop_gpiochip_set_names(gc, base);
+}
+EXPORT_SYMBOL_GPL(devprop_gpiochip_set_names_base);
+
 static unsigned long *gpiochip_allocate_mask(struct gpio_chip *gc)
 {
        unsigned long *p;
@@ -684,7 +698,7 @@ int gpiochip_add_data_with_key(struct gpio_chip
*gc, void *data,
        if (gc->names)
                ret = gpiochip_set_desc_names(gc);
        else
-               ret = devprop_gpiochip_set_names(gc);
+               ret = devprop_gpiochip_set_names(gc, 0);
        if (ret)
                goto err_remove_from_list;

diff --git a/drivers/gpio/gpio-mt7621.c b/drivers/gpio/gpio-mt7621.c
index 82fb20dca53a..d4f19ab726b2 100644
--- a/drivers/gpio/gpio-mt7621.c
+++ b/drivers/gpio/gpio-mt7621.c
@@ -282,6 +282,12 @@ mediatek_gpio_bank_probe(struct device *dev,
                return ret;
        }

+       ret = devprop_gpiochip_set_names_base(&rg->chip, bank * MTK_BANK_WIDTH);
+       if (ret) {
+               dev_err(dev, "Error setting line names for bank %d", bank);
+               return ret;
+       }
+
        /* set polarity to low for all gpios */
        mtk_gpio_w32(rg, GPIO_REG_POL, 0);

Best regards,
    Sergio Paracuellos

>
> --
> With Best Regards,
> Andy Shevchenko